Electric lamp



G. E. INMAN- Oct; 15, .1935'.

ELECTRIC LAMP Filed Jan. Z50,l 1955 2 Sheets-Sheet l :mangas:

Inventor: I

George E. Inman, b .Qq/j

Attorney.

oct. 1s, 193s. l G. E QNMAN A 2,011,719

ELEcmc LAMP Filed Jah. so, 193s `e sheets-sheet 2 Figi inventor: George E. Inman,

is Attorneg.

Patented Oct. 15)F 1935 UNITED STATES ELECTRIC LAMP George E. Inman, East Cleveland, Ohio, assignor to General Electric Company, a corporation of New York Application January 30, 1935, Serial No. 4,113 4 claims.` (01; 17e- 1) VMy invention relates to electric lamp units-generally and more particularly to such'units comprising two or more gaseous electric discharge lamp devices. i

vIn lamps known in the art as high pressure metal vapor arc lamps, such as the high pressure positive column mercury lamp, the arc voltagel increases after the starting of the lamp and reaches its full value after the lamp hasbeen operating an appreciable time. Such lamps have heretofore been used with a series resistance as a. ballast in the form of an incandescible iilament mounted externally of the container of the lamp. However, in such a, circuit 'the voltage l5 across the lament varies inversely with the arc voltage. Consequently, when the lament is designed to be heated toincandescence during the starting period of the arc discharge, the filament is not heated sulciently during the operating period of the lamp when the arc voltage increases and it is therefore a very inefficient light source. On the other handfif the lament is designed to be heated to incandescence during the operating period of the lamp, the filament is overloadedY Z5 during the starting period'when the arc voltage is low which causessaid filament tc burn out to terminate the useful life of the lamp unit. For example, for a lamp having electron emitting electrodes and operating on a 110 volt supply line,

the arc voltage during the first few minutes of operation would be about 12 and then after the lamp has warmed up. the voltage may be about 75. This means that the voltage across the lament would be about 98 for a few minutes and l5 then gradually decrease to 3,5, i. e., the change in voltage is almost three to one.

One of the objects of my invention is to provide a. lamp unit comprising a. combination of gaseousor vaporlamps which have opposite starting voltl0 age characteristics with a filament or filaments.

Another object is to provide such a lamp in which the lament is both an efiicient light source and has a long life. Another object is to provide an eicient lamp unit emitting mixed light of imi5 proved quality. Further objects and advantages of my invention will appear from the following description of species thereof.

`In accordance with these objects the new lamp unit comprises two or more gaseous or vapor elec- 0 tric discharge lamp devices having opposite startu ing voltage characteristics and a larnent, the

lamps and filament all being connected in series.

`One of the discharge devices may be a high pres sure metal vapor arclamp such as a high pres- '5 sure positive column mercury lamp, while another may be a low pressure positive column lamp or. the cathodic glow type of lamp, such as a sodium lamp. The voltage of a short low pressure lamp may be aboutduring the starting period and gradually decrease to about 25. 'I'he high pres- 5 sure arc lamp voltage is about 12 at the start of the arc discharge and increases to about 50. On

a volt line this makes a voltage variation in the filament of 4about 58 to 35, or less than two to one. A lament designed for such a. change gives l0 lsome useful light during operation without Aburn-- ing out during the starting period. Of course, for a higher line voltage two' or more low pressure lamps or one large one may be used in order to obtain a complete compensation and a very l5 eicient lamp. The combination of sodium, mercury and incandescent filament light is also very desirable because it produces the effect of white light.

In the drawings, Fig. 1 is a front elevation of a 20 lamp unit comprising my invention; Fig. 2 is a side elevation thereof; Fig. 3 is a plan view thereof; Fig. 4 is a somewhat diagrammatic elevation of a modied unit in which the envelope of .the low pressure positive column lamp is U'shaped; 25 Fig. 5 is a plan view thereof; Fig. 6 is a, somewhat diagrammatic elevation of a further modied unit comprising two low pressure lamps; and Fig. 7 is a plan view thereof.

Referring to Figs. 1-3, the lamp unit comprises 30 illustrated are of the internally emissive hollow 40 type and consist of a metal tube I1 which may be of nickel, secured at its rear end to an insu-` lating plug I8 and having a layer of electron emissive material I9, such as barium oxide, on its. inner surface. The upper and lower elec- 45 trodes I6 are mounted onleads 20, 2l respectively which extend through the plugs I8 to the interior of the tubes II and are electrically connected to said tubes by conducting strips 22. Each of the electrodes I6 also includes an internal heat- 50 ing resistance 23, the said resistances being connected by an axially extending conductor 24. The bulb I5 contains a diicultly vaporizable Working substance such as an alkali metal vapor like sodium, and operates with very small -vapor pres- I sures of such substance. pressure of the working substance is usually about 1 or 2 microns for sodium. The bulb also preferably contains a small amount of easily ionized gas likeneon or argon at a pressure of about 1 or 2 ,to 15 mm.to assist in starting the sodium or other vapor discharge.

The high pressure positive column lamp I2 comprises a tubular envelope or bulb 25 havingan electrode 26 at each end thereof mounted on upper and lower leads 21 and 28. The electrodesl 26 may consist of pressed and sintered refractory metal blocks or coils such as tungsten or nickel, impregnated with an electron emissive material such as barium oxide. The bulb 25l has a gaseous iilling therein consisting cf a readily ionizable starting gas, such as argon, and a readily. vaporizable material, preferably mercury, 29.

The upper lead 20 of the low pressure lamp I i is secured to one end of a lead 36, the other end of which is secured to the upper end of a longitudinally extending channel-shaped lead 3 I. The upper lead 21 of the high pressure lamp l2 is secured to one end of a lead 32, the opposite end of which is secured to the upper end of a second channel-shaped lead 33. The said channelshaped leads 3I, 33 extend downward into metal thimbles 34, 35 to which they are secured. The edges of said thimbles are sealed to tubular portions 36', 31 of a pressed glass cup 38, the'rim of which is fused to the neck of the outer envelope I0. The said envelope ID is evacuated at 39, and may be iilled with a gas if desired.

An end of the lower U-sliaped lead 2I of the low pressure lamp II .is secured to the lower end of the lament section i3, while an end of the lower U-shaped lead 28 of the high pressure lamp I2 is secured to the lower end of the iilament vsection I4. the upper ends of -the lament sec- .tions I3,` I4 are connected by an offset U-shaped conductor 46. The three elements: the low pressure lamp II, the high pressure lamp I2 and lament I3, I4, are thus connected in series.

When the above-described lamp is connected to the terminals of a current source, a circuit is established from the channel lead 3 I, through leads 30, 20, heater 23 of upper electrode I6 of lamp II, conductor 24, heater 23 of lower electrode I6, lead 2l, iilament section I3, conductor 40, filament I4, lead 26, to lower electrode 26 of the high pressure lamp I2, and from channel lead 33, through leads 32, 21 to upper electrode 26 of lamp I2. The line voltage impressed across the electrodes 26, 26 is suicient to ionize the starting gas in bulb 25 and the arc discharge starts between said electrodes 26. 26 as soon as the gaseous atmosphere is suiiciently ionized. As soon as the arc across electrodes 26, 26 starts, the voltage across them 'drops to about I2, a discharge is formed between the electrodes I6, I6 of the low pressure lamp I I and the voltage across them may be about 40. The voltage across the high pressure lamp I2 then starts toi rise and the Voltage across the low pressure lamp II starts to fall, thereby minimizing to a great extent the change in voltage across the filament I3, I4.

The modified lamp unit shown in Figs. 4 and 5 comprises an outer vacuum envelope or bulb 4I containing a high pressure positive column metal vapor lamp 42 like the lamp I2 in Figs. 1-3, preferably a mercury arc lanip, and comprising a straight tubular envelope or bulb-43 having an electrode 44 at each end, the upper electrode being mounted on a lead 45 and the lower electrode on a lead 46. The outer envelope also contains The absolute vapor a low pressure positive column lamp 41, preferably a sodium lamp. The ltubular envelope or bulb 46 of the lamp 41 is U-shaped and has an electrode 49 at each end thereof of the cold type, i. e., it does not have a heating resistance 6 adjacent thereto. The said electrodes 49 each vcomprise a metal tube having an electron emissive coating on the interior thereof the same as the electrodes I6 in Fig. 1. The left and right electrodes 49 are Amounted on leads 50, 5I respecl0 tively which are connected by a high resistance 52. A filament 53, preferably of tungsten, is located in the outer envelope 4I and is connected to the lead 45 at its upper end and to a lead 54 at -its lower end. The said filament 53 has been l5 offset to the right in Fig. 4 for the sake of clearness.

The starting circuit of the labove-described lamp unit is from lead 5I through resistance 52,

leads 50, 46, to lower electrode 44 of lamp 42 and 20 from lead 54 through lament 53, lead 45to upper electrode 44. The starting gas in lamp 42 is ionized and an arc discharge occurs between the electrodes 44 after which a discharge occurs between the electrodes 49 of lamp 41, the high re- 25 sistance being cut out of the circuit. Here again, after the arc discharges start, the voltage across the lamp 42 increases and the voltage across lamp 41 decreases, thereby cutting down the voltage differential across the filament 53 at the start and 30 during operation of the lamp.

The unit shown in Figs. 6 and '7 may be used where the line voltage is higher, and comprises an outer evacuated envelope 55 containing a high pressure positive column lamp 56; like the lamp I2 35 in Fig. 1, two low pressure` positive column lamps 51, 56 like the lamp II in Fig. 1, and filament sections 59, 60. The lower electrode 6I of low pressure lamp 56 is mounted on a lead 62 and the upper electrode 6I on a lead 63. The internal heat- 40 ing resistances (not'shown) of electrodes 6I. 6I are interconnected by a conductor 64. The lead 63 is connected to a cross lead 65 which is connected at each end to the upper ends of the rilament sections 59, 60. The lower ends of the said 45 l'ament sections are connected to a lead 66 which extends through the lower end of the bulb of lamp 56 and supports the lower electrode 61. The upper electrode 61 of lamp 56 is supported by a lead 68 which is connected by conductor 69 to the 50 lead 10 which supports the upper electrode 1I of the lamp 51. The internal beating resistance (not shown) of said upper electrode 1I is connected to the internal heating resistance (not shown) of lower electrode 1I by a conductor 12. 55

' The said lower electrode 1I is mounted on la lead The starting circuit of the above-described lamp is from lead 62, through the heatingv resistance (not shown) of lower electrode 6I, conductor 64, 60 heating resistance (not shown) of upper electrode 6I lead 63, conductor-65,1ilament branches 59, 60, lead 66, to lower electrode 61 of the high pressure lamp 56, and from lead 13 through heating resistance (not shown) of lower electrode 1I, con- 65 ductor 12, heating resistance (not shown) of upper electrode 1I, lead 10, conductory 69, lead 66. to upper electrode 61 of lamp 56. Here again, an arc discharge is established between-the electrodes 61 of high pressure lamp 56 and .then arc dis- 70 charges are established between the electrodes 6I 6I of low pressure lamp 58 and electrodes 1I, 1I, of the other low pressure lamp 51. The rising voltage characteristic of the high pressure lamp 56 is compensated by the drooping voltage char- 15 Vfilament ballast without the use of relays, thermostats or transformers or other external equipment. f

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A lamp unit comprising in combination, two or more gaseous electric discharge lamps each comprising van envelope containing a pair of electrodes. one of said lamps having a rising starting 4voltage characteristic and another of said lamps having a. drooping starting voltage characteristic, and an incandescible filament, the said lament and the gaps between the said electrodes of each of said discharge lamps being in series.

2. A lamp unit comprising in combination, a sealed outer envelope containing two or more gasecus electric discharge lamps each comprising an envelope containing a pair of electrodes, one of said lamps having a rising starting voltage characteristic and anotherof said lamps having a drooping starting voltage characteristic, and an incandescible filament disposed in said outer envelope, the said iilament and the gaps between the said electrodes of each of said discharge lamps being in series.

3. A lamp unit comprising in combination, two or more gaseous electric -discharge lamps each comprising an envelope containing a pair of electrodes, one of said lamps being a high pressure lamp and having -a rising starting voltage characteristic and another of said lamps being a low pressure lamp and having 'a drooping starting voltage characteristic, and an incandescible filament, the said filament and the gaps between the said electrodes of cach of said discharge lamps being in series.

4. A lamp unit comprising in combination, two

or more gaseous electric discharge lamps each comprising an envelope containing a pair of electrodes, one of said lamps being a high pressure mercury lamp and having a rising starting voltage characteristic and another of said lamps being a. low pressure sodium lamp and having a drooping starting voltage characteristic, and an' incandescible filament, the said iilamentand the gaps between the said electrodes of each of said discharge lamps being in series.

' GECRGE E. INMAN. 

